Circadian Rhythms as a Basis for Work Organization

2012 ◽  
Vol 55 (1) ◽  
pp. 204-217 ◽  
Author(s):  
Lia Buarque de Macedo Guimarães ◽  
Jose Luis Duarte Ribeiro ◽  
Tarcísio Abreu Saurin ◽  
Paulo Ivo Homem de Bittencourt
Keyword(s):  
Circadian Rhythms ◽  
Human Performance ◽  
Work Organization ◽  
Task Demands ◽  
Work Design ◽  
Biological Clocks ◽  
Mental Demands ◽  
Physiological Markers ◽  
New System ◽  
The Ideal

Objective: With the assumption that circadian rhythms influence human performance, the work of live line electricians was reorganized and evaluated. The hypothesis was that in highly physical and attention-demanding work, the organization of tasks, according to the ideal period of day and day of week, should diminish stress and consequent work risks. Background: There are only a few studies reporting the work of electricians and even fewer approaching work organization. Moreover, these investigations often do not consider human physiological limitations and capabilities as well as task demands. Method: A new work system was proposed with consideration of (a) the circadian cycles and homeostatic processes; (b) the effect of heat, which is a zeitgeber (synchronizer) for the biological clocks; and (c) the degree of physical and mental demands of the different performed tasks, which was assessed on the basis of opinions of the electricians and physiological markers of stress that are controlled by circadian rhythms. The traditional and new systems were compared on the basis of two cognitive indices (the arrangement of matchsticks and the perception of a minute) and three physiological markers of mental-to-physical loads (heart frequency and the level of adrenaline and noradrenaline). Results: Both physical and mental loads were reduced in the new system. Conclusion: Work organization should include consideration of human circadian rhythms, mainly when stressful and high-risk tasks are involved. Application: The findings can be applied in any work design, but they are especially suited for highly demanding work carried out outdoors.

Circadian tuning of motivation. A little organ of yesterday?

1995 ◽  
Vol 7 (2) ◽  
pp. 21-23 ◽  
Author(s):  
S. Daan
Keyword(s):  
Internal State ◽  
External Environment ◽  
Animal Behaviour ◽  
The Body ◽  
Biological Clocks ◽  
Motivational Systems ◽  
Regulatory Principle ◽  
The Face ◽  
Temporal Organisation ◽  
The Ideal

The analysis of motivational systems underlying temporal organisation in animal behaviour has relied primarily on two conceptual functional frameworks: Homeostasis and biological clocks. Homeostasis is one of the most general and influential concepts in physiology. Walter Cannon introduced homeostasis as a universal regulatory principle which animals employ to maintain constancy of their ‘internal milieu’ in the face of challenges and perturbations from the external environment. Cannon spoke of “The Wisdom of the Body”, the collective of responses designed to defend the ideal internal state against those perturbations.

scholarly journals Composite hollow truss with multiple vierendeel panels

2013 ◽  
Vol 66 (4) ◽  
pp. 431-438
Author(s):  
Augusto Ottoni Bueno da Silva ◽  
Newton de Oliveira Pinto Júnior ◽  
João Alberto Venegas Requena
Keyword(s):  
Bearing Capacity ◽  
Failure Modes ◽  
Three Dimensional ◽  
Analytical Calculation ◽  
Two Dimensional ◽  
Shear Forces ◽  
Vertical Displacements ◽  
New System ◽  
The Ideal

The aim of this study was to evaluate through analytical calculation, two-dimensional elastic modeling, and three-dimensional plastic modeling, the bearing capacity and failure modes of composite hollow trusses bi-supported with a 15 meter span, varying the number of central Vierendeel panels. The study found the proportion span/3 - span/3 - span/3, as the ideal relationship for the truss - Vierendeel - truss lengths, because by increasing the proportion of the length occupied by the central Vierendeel panels, the new system loses stiffness and no longer supports the load stipulated in the project. Furthermore, they can start presenting excessive vertical displacements and insufficient resistance to external shear forces acting on the panels.

Design of Measurement System of the Center of Gravity

2013 ◽  
Vol 706-708 ◽  
pp. 733-736
Author(s):  
Fang Li
Keyword(s):  
Measurement System ◽  
Center Of Gravity ◽  
Actual Position ◽  
Ideal Position ◽  
The Future ◽  
The Difference ◽  
New System ◽  
The Ideal

It is very difficult to confirm the position of the center of gravity irregular object.This paper introduces a new system,which can be used in measuring and adjusting of the center of gravity.The irregular object was put on the support parts,then the center of gravity was given.When the actual position was compared with the ideal position,the difference was given. Until actual position and ideal position were coincided,the machining was continuing. Matlab was programmed in this measure system. It will be applied widely in the future.

scholarly journals Tactile orientation perception: an ideal observer analysis of human psychophysical performance in relation to macaque area 3b receptive fields

2015 ◽  
Vol 114 (6) ◽  
pp. 3076-3096 ◽  
Author(s):  
Ryan M. Peters ◽  
Phillip Staibano ◽  
Daniel Goldreich
Keyword(s):  
Cortical Neurons ◽  
Human Performance ◽  
Spatial Perception ◽  
Receptive Fields ◽  
Human Perception ◽  
Ideal Observer ◽  
Orientation Discrimination ◽  
Orientation Perception ◽  
Area 3B ◽  
The Ideal

The ability to resolve the orientation of edges is crucial to daily tactile and sensorimotor function, yet the means by which edge perception occurs is not well understood. Primate cortical area 3b neurons have diverse receptive field (RF) spatial structures that may participate in edge orientation perception. We evaluated five candidate RF models for macaque area 3b neurons, previously recorded while an oriented bar contacted the monkey's fingertip. We used a Bayesian classifier to assign each neuron a best-fit RF structure. We generated predictions for human performance by implementing an ideal observer that optimally decoded stimulus-evoked spike counts in the model neurons. The ideal observer predicted a saturating reduction in bar orientation discrimination threshold with increasing bar length. We tested 24 humans on an automated, precision-controlled bar orientation discrimination task and observed performance consistent with that predicted. We next queried the ideal observer to discover the RF structure and number of cortical neurons that best matched each participant's performance. Human perception was matched with a median of 24 model neurons firing throughout a 1-s period. The 10 lowest-performing participants were fit with RFs lacking inhibitory sidebands, whereas 12 of the 14 higher-performing participants were fit with RFs containing inhibitory sidebands. Participants whose discrimination improved as bar length increased to 10 mm were fit with longer RFs; those who performed well on the 2-mm bar, with narrower RFs. These results suggest plausible RF features and computational strategies underlying tactile spatial perception and may have implications for perceptual learning.

Photic Response Parameters of Circadian Rhythms in The Spinifex Hopping Mouse, Notomys alexis.

1996 ◽  
Vol 19 (1) ◽  
pp. 11
Author(s):  
A.J.P. Francis ◽  
G.J. Coleman
Keyword(s):  
Circadian Rhythms ◽  
Phase Relations ◽  
Constant Light ◽  
Constant Darkness ◽  
Biological Clocks ◽  
Circadian Activity ◽  
Activity Rhythms ◽  
Controlled Conditions ◽  
Australian Native Rodent ◽  
Photic Response

Circadian rhythms are generated endogenously by biological clocks or 'pacemakers', which are responsive to significant environmental stimuli termed zeitgebers. Interactions between pacemakers and zeitgebers provide the basis for synchronisation by light-dark (LD) cycles, and the characteristics of each of these elements determines the phase-relations maintained between an animal's circadian activity rhythms and the natural temporal environment. We report here the basic photic response parameters for an Australian native rodent, Notomys alexis. Under controlled conditions of constant darkness or constant light, N. alexis were found to 'free-run', and with periods different from 24 hours. Under LD cycles N. alexis were strictly nocturnal although, compared to other rodents, entrainment to LD cycles was relatively unstable. This may indicate that N. alexis are not strongly dependent on the LD cycle as a zeitgeber.

scholarly journals Genetic variation and phenotypic plasticity in circadian rhythms in an armed beetle, Gnatocerus cornutus (Tenebrionidae)

2020 ◽  
Vol 130 (1) ◽  
pp. 34-40 ◽  
Author(s):  
Kentarou Matsumura ◽  
Masato S Abe ◽  
Manmohan D Sharma ◽  
David J Hosken ◽  
Taishi Yoshii ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Phenotypic Plasticity ◽  
Circadian Rhythms ◽  
Temperature Effects ◽  
Temperature Compensation ◽  
Biological Rhythms ◽  
Total Activity ◽  
Biological Clocks ◽  
Isofemale Lines ◽  
Free Running

Abstract Circadian rhythms, their free-running periods and the power of the rhythms are often used as indicators of biological clocks, and there is evidence that the free-running periods of circadian rhythms are not affected by environmental factors, such as temperature. However, there are few studies of environmental effects on the power of the rhythms, and it is not clear whether temperature compensation is universal. Additionally, genetic variation and phenotypic plasticity in biological clocks are important for understanding the evolution of biological rhythms, but genetic and plastic effects are rarely investigated. Here, we used 18 isofemale lines (genotypes) of Gnatocerus cornutus to assess rhythms of locomotor activity, while also testing for temperature effects. We found that total activity and the power of the circadian rhythm were affected by interactions between sex and genotype or between sex, genotype and temperature. The males tended to be more active and showed greater increases in activity, but this effect varied across both genotypes and temperatures. The period of activity varied only by genotype and was thus independent of temperature. The complicated genotype–sex–environment interactions we recorded stress the importance of investigating circadian activity in more integrated ways.

scholarly journals Melatonin administration can entrain the free-running circadian system of blind subjects

2000 ◽  
Vol 164 (1) ◽  
pp. R1-R6 ◽  
Author(s):  
SW Lockley ◽  
DJ Skene ◽  
K James ◽  
K Thapan ◽  
J Wright ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Core Body Temperature ◽  
Circadian System ◽  
Melatonin Treatment ◽  
Circadian Phase ◽  
Melatonin Administration ◽  
Free Running ◽  
Physiological Markers ◽  
Core Body ◽  
First Time

Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind design, five subjects received placebo or 5 mg melatonin p.o. daily at 2100 h for a full circadian cycle (35-71 days). The remaining two subjects also received melatonin (35-62 days) but not placebo. Urinary aMT6s and cortisol (n=7) and core body temperature (n=1) were used as phase markers to assess the effects of melatonin on the During melatonin treatment, four of the seven free-running subjects exhibited a shortening of their cortisol circadian period (tau). Three of these had taus which were statistically indistinguishable from entrainment. In contrast, the remaining three subjects continued to free-run during the melatonin treatment at a similar tau as prior to and following treatment. The efficacy of melatonin to entrain the free-running cortisol rhythms appeared to be dependent on the circadian phase at which the melatonin treatment commenced. These results show for the first time that daily melatonin administration can entrain free-running circadian rhythms in some blind subjects assessed using reliable physiological markers of the circadian system.

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